Stop all Explorer.exe instances, delete the user's hidden IconCache.db file, and restart Explorer.

or even better Download this small utility http://www.solidpost.com/Telechargement/ReIconCache.exe to rebuild the icon cache

(There are other ways as well) :

1. Close all Explorer windows that are currently open.
2. Launch Task Manager using the CTRL+SHIFT+ESC key sequence, or by running taskmgr.exe.
3. In the Process tab, right-click on the Explorer.exe process and select End Process.
4. Click the End process button when asked for confirmation.
5. From the File menu of Task Manager, select New Task (Run…)
6. Type CMD.EXE, and click OK
7. In the Command Prompt window, type the commands one by one and press ENTER after each command :
8. CD /d %userprofile%\AppData\Local
9. DEL IconCache.db /a
10. EXIT
11. In Task Manager, click File, select New Task (Run…)
12. Type EXPLORER.EXE, and click OK.